PHP - 中斷或暫停pthread的執行

Question

如何在主要上下文中中斷線程的執行？

在下面的代碼片段中 - 如何停止線程在不破壞它的情況下執行的操作？

class ReadFileThread extends Thread 
{ 
    public function __construct($file, $chunk = 1024) 
    { 
     $this->file = $file; 

     $this->chunk = $chunk; 
    } 

    public function run() 
    { 
     if(is_file($this->file) && is_readable($this->file)) 
     { 
      $fh = fopen($this->file, 'rb'); 

      while(!feof($fh)) 
      { 
       $content = fread($fh, $this->chunk); 
      } 

      fclose($fh); 
     } 
    } 
} 

$num = 10; 
$threads = []; 

for($i = 0; $i < $num; $i++) 
{ 
    $thread = new ReadFileThread('/path/to/10gig_file.txt', 1024); 

    $threads[] = $thread; 

    // I start the thread, now it's detached from the main context and is reading the file asynchronously 
    $thread->start(); 
} 

// The interesting part - I want to random 1 thread whose operation of file reading I want to interrupt 
$to_interrupt = $threads[rand(0, $num)]; 

// How to interrupt the thread without destroying it? I want its context preserved 

Answer 1

RandomSeeds答案是接近，但開放的競爭條件。

<?php 
class FileReader extends Thread { 
    public $file; 
    public $pause; 

    public function __construct($file) { 
     $this->file = $file; 
     $this->pause = false; 
    } 

    public function run() { 
     if (($handle = fopen($this->file, "rb"))) { 
      $len = 0; 
      do { 
       $this->synchronized(function(){ 
        if ($this->paused) { 
         printf(
          "\npausing %lu ...\n", $this->getThreadId()); 
         $this->wait(); 
        } 
       }); 

       $data = fread($handle, 1024); 
       $len += strlen($data); 

       if (($len % 2) == 0) { 
        printf( 
         "\r\rread %lu", $len); 
       } 
      } while (!feof($handle)); 

      fclose($handle); 
     } 
    } 

    public function pause() { 
     return $this->synchronized(function(){ 
      return ($this->paused = true); 
     }); 
    } 

    public function unpause() { 
     return $this->synchronized(function(){ 
      $this->paused = false;  
      if ($this->isWaiting()) { 
       return $this->notify(); 
      } 
     }); 
    } 
} 

function do_something($time) { 
    $start = time(); 

    while (($now = time()) < ($start + $time)) { 
     usleep(100); 
     if (($now % 2) == 0) { 
      echo "."; 
     } 
    } 

    echo "\n"; 
} 

$reader = new FileReader("/path/to/big/file.ext"); 
$reader->start(); 

sleep(2); 
$reader->pause(); 
do_something(rand(2, 4)); 
$reader->unpause(); 
sleep(2); 
$reader->pause(); 
do_something(rand(2, 4)); 
$reader->unpause(); 
sleep(2); 
$reader->pause(); 
do_something(rand(2, 4)); 
$reader->unpause(); 
?> 

是用於同步的目的變量只能用在synchronized塊訪問是非常重要的，我已經省略了停止執行/退出功能，但它的邏輯是大致相同的，因爲RandomSeeds例所示。

競爭條件潛伏中：

public function mine($data) { 
    /* anyone can set doSynchronization at any time */ 
    if ($this->doSynchronization) { 

     $this->synchronize(function(){ 
      /* checking the predicate in here is safer */ 
      $this->wait(); 
     }); 
    } 
} 

好：

public function mine($data) { 
    $this->synchronize(function(){ 
     if ($this->doSynchronization) { 
      $this->wait(); 
     } 
    }); 
} 

極端：

public function mine($data) { 
    $this->synchronize(function(){ 
     while ($this->doSynchronization) { 
      $this->wait(); 
     } 
    }); 
} 

POSIX標準總是有你寫的極端方式，我沒有那麼臃腫，無論對你有用。這個極端代碼的原因是，必須允許線程接收除正在等待的信號之外的信號，許多低級信號可能會導致線程從調用pthread_cond_wait中喚醒;在循環中檢查謂詞，防止規範稱爲虛假喚醒......但這種極端措施也會導致不良副作用;那些線程收到低電平信號的原因是因爲它們需要採取某種行動，忽略這一點很容易導致堆棧的不同部分發生死鎖，因爲它預期線程死掉（或者做其他事情，模具是一個例子），當它發出信號...

Answer 2

從來沒有使用pthreads，tbh，但你有沒有嘗試在線程類中做一個公共布爾標誌？

Answer 3

AFAIK您不能任意暫停併發線程，但可以向其發送通知。另一個線程在收到通知時必須合作並自願暫停。

例子：

<?php 

class MyThread extends Thread { 

    private $pauseRequested = false; 
    private $stopRequested = false; 

    public function pause() { 
     $this->synchronized(function($thread){ 
      $thread->pauseRequested = true; 
     }, $this); 
    } 

    public function resume() { 
     $this->synchronized(function($thread){ 
      $thread->pauseRequested = false; 
      $thread->notify(); 
     }, $this); 

    } 

    public function stop() { 
     $this->synchronized(function($thread){ 
      $thread->stopRequested = true; 
     }, $this); 
    } 

    public function run() { 
     echo 'Thread started!' . PHP_EOL; 
     while (!$this->stopRequested) { 

      // do the actual work 
      echo 'Working...'; 
      sleep(1); 

      // check if we have been requested to pause 
      $this->synchronized(function($thread){ 
       if ($this->pauseRequested) { 
        echo 'Paused...'; 
        $thread->wait(); // this is where the magic happens 
       } 
      }, $this); 
     } 

     if ($this->stopRequested) { 
      echo PHP_EOL . 'Stopped!' . PHP_EOL; 
     } 
    } 
} 


$t = new MyThread(); 
$t->start(); 
sleep(5); 

$t->pause(); 
sleep(2); 

$t->resume(); 
sleep(5); 

$t->stop(); 

// wait for $t to complete 
$t->join(); 

?>